Crystal structure analyses, band calculations, and electrical resistivity and magnetic susceptibility measurements have been carried out for new θ-type BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene; abbreviated as ET] salts, θ-(BEDT-TTF)2TlCo(SCN)4 and θ-(BEDT-TTF)2TlZn(SCN)4 [abbreviated as θ-TlCo and θ-TlZn], as well as crystal structure analyses of θ-(BEDT-TTF)2RbM′(SCN)4 [M′ = Co, Zn; abbreviated as θ-RbM′]. θ-TlCo and θ-RbM′ [M′ = Co, Zn] are isostructural to the previously reported θ-CsM′, and the metal-insulator transition temperature increases from 20 K (θ-CsM′ [M′ = Co, Zn]), 190 K (θ-RbM′) to 250 K (θ-TlCo) with decreasing the unit cell volume, namely, the inverse chemical pressure effect. A structural investigation for θ-RbM′ [M′ = Co, Zn] indicates a lattice a modulation at the metal-insulator transition temperature (190 K). For the other salt, θ-TlZn, a semiconductor–semiconductor transition has been observed at 165 K, where the behavior of the magnetic susceptibility, following the two-dimensional Heisenberg model, changes from J = −30 K to −57 K under a slow cooling condition.
对新型θ型BEDT-
TTF[双(乙二
硫)
四硫富瓦烯;进行了晶体结构分析、能带计算以及电阻率和磁化率测量。缩写为 ET] 盐、θ-(BEDT-
TTF)2TlCo(SCN)4 和 θ-(BEDT-
TTF)2TlZn(SCN)4 [缩写为 θ-TlCo 和 θ-TlZn],以及晶体结构分析θ-(BEDT-
TTF)2RbM′(SCN)4 [M′ = Co, Zn;缩写为θ-RbM′]。 θ-TlCo 和 θ-RbM′ [M′ = Co, Zn] 与之前报道的 θ-CsM′ 是同构的,
金属-绝缘体转变温度从 20 K 开始增加 (θ-CsM′ [M′ = Co, Zn] ]),随着晶胞体积的减小,从190 K(θ-RbM′)到250 K(θ-TlCo),即逆
化学压力效应。 θ-RbM′ [M′ = Co, Zn] 的结构研究表明在
金属-绝缘体转变温度 (190 K) 下存在晶格 a 调制。对于另一种盐 θ-TlZn,在 165 K 时观察到半导体-半导体转变,其中磁化率的行为遵循二维海森堡模型,在一定温度下从 J = -30 K 变为 -57 K。缓慢冷却条件。